Vat dyeing of acrylonitrile textile materials



Patented July 13, 1954 UNITED STATES ENT ()FFICE VAT DYEING OF ACRYLONITRILE TEXTILE MATERIALS nonprofit trust N Drawing. Application November 24, 1950, Serial No. 197,512

6 Claims.

"1 The present invention relates to the dyeing of textile materials based on polyacrylcnitrile or acrylonitrile polymer fibers. A brand of polyacrylonitrile textile materials is available on the market under the trade-mark Orlon.

The satisfactory dyeing of polyacrylonitrile textile materials has been a persistent problem. Textile materials based on polyacrylonitrile fibers are characterized by the resistance which they exhibit to coloration by many different classes of 1 impractical, expensive, diificult to control, and,

in many cases, have led to deterioration of the polyacrylonitrile textile material. Thus, to produce heavy black, brown, and maroon shades, it has been proposed to dye at the boil with vat dyes using a high concentration of caustic. But this results in damage to the fiber.

In the article by Robert J. Thomas and Paul L. Meunier, American Dyestuif Reporter 38, pages P925-932, December 12, 1949, entitled The dyeing of Orion acrylic fiber and its use in colored textiles, at page P927, it is stated that: Orlon acrylic continuous filament fiber exhibits an aihnity for most indigoid and thioindigoid vat dyes at 212 F. The anthraquinone vat colors,

on the other hand, exhibit virtually no affinity for the continuous filament. The degree of exhaustion of the indigoids and thioindigoids is markedly improved by incorporating high concentrations of potassium salts, e. g., potassium carbonate, in the dye liquor. Essentially no penetration of the fiber occurs at 212 F. and the fastness to cracking is poor except in light shades which have been subjected to a rigorous soaping subsequent to oxidation. The greatest deterrent to the commercial use of vat dyes, however, is their tendency when applied in heavy shades to deposit unevenly on the yarn and fabric.

In accordance with the present invention, I have found that polyacrylonitrile textile materials can be dyed evenly in medium to heavy shades with vat dyes, and without any undue damage to the fiber, if the textile material, after thorough padding of the unreduced vat dye thereon, is introduced into a reducing oath which contains a high concentration of sodium carbonate, e. g., about 30 per cent. If the sodium carbonate is added to the reducing bath after introduction of the textile material, a very weak shade and poor penetration results since the padded pigment has a tendency to leach out from the textile material into the reducing bath and will not salt out again onto the textile material upon addition of the sodium carbonate.

A preferred method of practicing the process of my invention comprises subjecting, as by padding, polyacrylonitrile textile material over a prolonged period of time to a dispersion of the unreduced vat dye maintained at a temperature of at least 11, and preferably at the boil; subjecting the impregnated textile to a reducing bath maintained at an elevated temperature, preferably at the boil, and composed of a small amount of sodium hydroxide, e. g., about 1 per cent, a small amount of sodium hydrosulfite, e. g., about 1 per cent, and a high concentration of sodium carbonate, e. g., about 30 per cent, until reduction is complete, then subjecting the treated material to an oxidation bath preferably maintained at the boil which may be composed of hydrogen peroxide and acetic acid; and finally soaping the dyed textile, preferably at the boil. After soaping, the cloth may be rinsed and dried.

It is surprising that high concentrations of sodium carbonate can be employed in the reduction bath to effect salting out of the dyestufi on the fabric and assist the dyeing. In the Thomas et a1. process, potassium carbonate is added after the cloth has been entered into the reducing bath. These authors state that they experimented with many salts other than potassium salts to get the same effect, but failed. I have attempted to use a high concentration of potassium carbonate according to the procedure of my invention, but the shade of the dye was adversely affected in that considerable bronzing occurred. Likewise, when sodium sulfoxylate formaldehyde was employed in the reducing bath, I was unable to obtain dark shades and good penetration of the vat dyes.

To obtain optimum results when practicing my novel process, it is advantageous to maintain the vat pigment dispersion and the reducing bath at the boil. When the vat pigment dispersion is applied by padding, the fabric should be padded repeatedly through the boiling padding liquor to 3 insure thorough penetration. The cloth is padded to 100 per cent liquor retention. In case of dyeing by immersion, the textile material should. be immersed over a prolonged period of time, e. g., about five minutes to about one hour.

The concentration of the vat pigment employed is determined by the depth of shade de sired, larger concentrations being employed when deeper shades are desired than when light or medium shades are to be obtained. To complete the reduction, the reducing bath is maintained at the boil for about five minutes to about one hour depending on the vat dyestuif employed. The oxidation treatment at the boil requires about five to about ten minutes to develop the reduced dye.

By the novel procedure of the present invention, vat dye-stuifs which are stable under the conditions employed readily yield medium to heavy even shades on polyacrylonitrile textile materials. Illustrative of the vat dyes which may be used to give highly satisfactory dyeings on polyacrylonitrile textiles when applied according to the process of my invention are those listed hereinafter. The vat dyes are identified by their Colour Index (C. I.) numbers or their Foreign Prototype (Pr.) numbers where these are available, and by their commercial names and name of manufacturer where there is no C. I. or Pr. number: C. I. Nos. 1101, 1170, 1217, 1186, 1212, 1184 and 1098; Fr. Nos. 9, 109, and 121; Calcosol Copper Brown Paste (American Cyanamid Co.) Algol Deep Black BDA Extra (General Dyestufi Corp); Sulfanthrene Black PG Double Paste, Sulfanthrene Black PR Double Paste, Sulfanthrene Scarlet 2BP Paste, Sulfanthrene Red-Violet 2RN Paste, and Flavone Yellow R Paste (E. I. du Pont de Nemours & 00.). The dyes can be employed individually or in mixtures of two or more dyes.

The following examples will serve to illustrate the invention, it being understood, however that the invention is not limited thereto.

Example 1 A pad liquor is prepared by dispersing parts by weight of Ponsol Jade Green Supra Double Paste (C. I. No. 1101) in 85 parts by weight of water. The pad liquid is then brought to and maintained at the boil. The polyacrylonitrile cloth is padded at least five times through the boiling pad liquor. After padding, the cloth is introduced into an aqueous boiling reduction bath composed of 1 per cent sodium hydroxide, 1 per cent sodium hydrosulfite, and per cent sodium carbonate. The cloth is subjected to the boiling reduction bath until reduction of the vat dye is complete which takes about 15 minutes. After reduction is complete, the cloth is introduced into an aqueous oxidizing bath containing 1 per cent of hydrogen peroxide and 1 per cent of acetic acid. The oxidation is preferably carried out at the boil for about 5-10 minutes. The cloth is then soaped with a 3 per cent soap solution at the boil, rinsed, and dried. Two soapings at the boil have been found to remove excess surface dye and to improve the crock fastness properties of the dyed polyacrylonitrile fabric. A heavy shade of green was obtained on the fabric.

Example 2 A pad liquor is prepared by adding 80 parts by weight of Sulfanthrene Black PG Double Paste with good stirring to 120 parts by weight of water. Polyacrylonitrile cloth is dyed therewith 4 by the procedure of Example 1. A heavy black coloration is obtained.

Example 3 A pad liquor is prepared by stirring 38 parts by weight of Sulfanthrene Black PG Double Paste and 2 parts by weight of Ponsol Jade Green Supra Double Paste in 60 parts by weight of water. Polyacrylonitrile fabric is dyed therewith by the procedure of Example 1. A heavy black shade is obtained.

Example 4 A pad.liquor is prepared by stirring 20 parts of Sulfanthrene Black PR Double Paste, 12 parts of Ponsol Flavone-Yellow GC Double Paste (Pr. 9) and 8 parts of Ponsol Jade Green Supra Double Paste in 60 parts of water (all parts being by weight). Polyacrylonitrile cloth is dyed therewith by the procedure of- Example 1. A heavy even dyeing was obtained.

The following is claimed:

1. A process for evenly dyeing in medium and heavy shades a textile material comprising acrylonitrile polymer, which comprises treating said material with a dispersion of an unreduced vat dye at the boil, introducing the treated material into a reducing bath at the boil composed of sodium hydroxide, sodium hydrosulfite, and about a 30 per cent concentration of sodium carbonate, and subjecting the thus treated material to an oxidizing bath to develop the vat dye.

2. A process as in claim 1, wherein the dispersion of the vat dye is repeatedly padded on to the acrylonitrile polymer prior to being introduced into the reducing bath.

3. A process as in claim 1, wherein the reducing bath is composed of about 1 per cent sodium hydroxide, about 1 per cent sodium hydrosulfite, and about 30 per cent sodium carbonate, and the oxidizing bath is composed of about 1 per cent hydrogen peroxide and about 1 per cent acetic acid.

4. A process for evenly dyeing in medium and heavy shades an article composed of polyacrylonitrile fiber, which comprises padding such article with a dispersion of an unreducecl vat dye, introducing the padded material into a reducing bath composed of sodium hydroxide, sodium hydrosulfite, and about a 30 per cent concentration of sodium carbonate, and subjecting the thus treated material to an oxidizing bath to develop the dye, all the treatments being carried out at the boil.

5. A process for evenly dyeing in medium and heavy shades a textile material composed of acrylonitrile polymer, which comprises treating said material with a dispersion of an unreduced vat dye at a temperature above F. introducing the impregnated textile material into a reducing bath at the boil composed of sodium hydroxide, sodium hydrosulfite, and about a 30 percent concentration of sodium carbonate which is present in the solution at the time of introduction of the impregnated textile material into the reducing bath, and subjecting the thus treated material to an oxidizing bath to develop the vat dye.

6. A process for evenly dyeing in medium and. heavy shades a textile material composed of polyacrylonitrile fiber, which comprises repeatedly padding the material with a dispersion of an unreduced vat dye, introducing the padded material into a reducing bath composed of sodium 5 6 hydroxide, sodium hydrosulfite, and about a 30 OTHER REFERENCES per cent concentration of sodium carbonate, and Dyeing of Orlon Acrylic Fiber and Its Use in subjecting the thus treated material to an oxi- Colored Te tiles article b Thom S and dizing bath to develop the dye, all the treatments Meunier in g Dyestufi Repxgrter for g being carried out at the boil. 5 her 12 1949 P925 to P928 References Cited in the file of this patent American Dyestufi Reporter for January 10,

FOREIGN PATENTS 1949, pages P9, P10.

Number Country Date 578,212 Great Britain June 19, 1946 10 

1. A PROCESS FOR EVENLY DYEING IN MEDIUM AND HEAVY SHADES AT TEXTILE MATERIAL COMPRISING ACRYLONITRILE POLYMER, WHICH COMPRISES TREATING SAID MATERIAL WITH A DISPERSION OF AN UNREDUCED VAT DYE AT THE BOIL, INTRODUCING THE TREATED MATERIAL INTO A REDUCING BATH AT THE BOIL COMPOSED OF SODIUM HYDROXIDE, SODIUM HYDROSULFITE, AND ABOUT A 30 PER CENT CONCENTRATION OF SODIUM CARBONATE, AND SUBJECTING THE THUS TREATED MATERIAL TO AN OXIDIZING BATH TO DEVELOP THE VAT DYE. 